In the ferrous and nonferrous molten metals industries, ladles and similar metal receivers such as holding vessels and vacuum furnace chambers, receive a charge of molten metal. The receivers usually are lined with a refractory material, and it is desirable to preheat the receiver before molten metal is received in the receiver in order to avoid interface solidification of the metal upon contact between the metal and the cold interior surface of the receiver, and also to avoid thermal shock to the refractory liner of the receiver, thus avoiding deterioration of the liner. A preheated ladle also minimizes the heat loss from the molten metal as the metal is transported in the ladle from the furnace to the pouring position, thereby assisting in maintaining the molten metal at a high enough temperature for use in a casting machine or mold.
A common prior art method for heating ladles and other molten metal receivers prior to charging them with molten metal is to direct an open natural gas flame into the open chamber of the ladle. The open flame heating method permits combustion gases from within the ladle chamber to escape to the surrounding atmosphere. This permits a substantial amount of the heat energy to escape without effective use thereof, thus wasting an excessive amount of gas. Moreover, it is difficult to uniformly heat a ladle with an open flame, in that the ladle may be overheated in some areas and not heated sufficiently in other areas. Additionally, after a ladle has been initially heated, it is sometimes desirable to maintain the ladle in its heated condition if the ladle achieves its desired temperature before it is time to introduce the molten metal to the ladle. In this situation the open flame heating procedure continues to waste energy and hot spots are more likely to be formed in the ladle.